Echocardiography is an imaging modality that takes advantages of the physical properties of sound. In echocardiography, sound pulses generated by a transducer travel through the thoracic cavity, reflect off structures around and in the heart, and return to the transducer, and are processed into images. This is similar to the way sound behaves in a canyon - as sound travels through the canyon, it is reflected off the walls of the canyon and returns to the original source as an echo. The sound pulses used in echocardiography are in the ultrasound range, or greater than 20,000 cycles per second (20 KHz), and are higher than the sound audible to humans, which is in the 20-20,000 Hz range. Several mammalian species use ultrasound to locate other animals and prey, including bats, dolphins, whales, and some fish. They take advantage of the following properties of ultrasound: it can be directed and focused, travels at different speeds through different media allowing for the discrimination of types of objects, and follows the laws of reflection and refraction. Similarly, ultrasound beams can be used in medical imaging and echocardiography.
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